The present invention relates to an arrangement for stabilizing the flow of the fuel-air mixture in a carburetor. More particularly, this invention concerns the stabilization of flow in a reaction carburetor of the type containing one or more catalysts for the catalytic conversion of liquid into gaseous fuel.
A known technique for reducing the emission of noxious substances in the exhaust gases of internal combustion engines consists in supplying the fuel needed for combustion in gaseous form. In comparison to internal combustion engines operated on liquid fuel, engines which are provided with a proper mixture of air and gaseous fuel are capable of complete combustion independently of the engine operating condition. This improved combustion is due to the fact that the gaseous fuel remains in the gaseous aggregate condition even at low temperatures. Thus, for example, during a cold start of the internal combustion engine, condensation will not form on the cold cylinder walls as is the case with internal combustion engines operating on liquid or vaporized fuel.
In view of the difficulty and expense of carrying gaseous fuel on vehicles, even in the form of gases that are liquefied under pressure, it has already been proposed that the gaseous fuel required for combustion be prepared in a reaction carburetor on the intake side of an internal combustion engine by catalytic and thermal reaction from the liquid fuel customarily used in internal combustion engines. In a reaction carburetor, a mixture of air and partially vaporized liquid fuel (or of air, exhaust gases and liquid fuel) flows through one or more catalysts arranged in series in which the liquid or vaporized fuel is converted at higher temperatures (e.g., 200.degree. to 1,000.degree. C., depending upon the catalysts used) into gaseous fuel by partial combustion. Complete combustion is avoided, in part due to a lack of a sufficient quantity of air.
In reaction carburetors of this kind, there is a danger that the sensitive catalysts will be locally overheated, and thereby destroyed, through flame formation. The generation of flames in the fuel-air mixture is determined at high temperatures essentially by the flow condition. For example, a turbulent or uneven flow leads to flame formation whereas the generation of flames can be prevented if a laminar flow profile is maintained within the carburetor.